Feasibility study of using a travelling CO 2 and CH 4 instrument to validate continuous in-situ measurement stations

Transcription

1 Feasibility study of using a travelling CO 2 and CH 4 instrument to validate continuous in-situ measurement stations S. Hammer 1, G. Konrad 1, A. Vermeulen 2, M. Delmotte 3, A. Jordan 4, L. Hazan 3, D. Griffith 5 and I. Levin 1 1 Institut für Umweltphysik (IUP), University of Heidelberg, Germany 2 Netherlands Energy Research Foundation (ECN), Petten, The Netherlands 3 Laboratoire des Sciences du Climat et de l'environnement (LSCE), Gif-sur-Yvette, France 4 Max Planck Institute for Biogeochemistry, Jena, Germany 5 School of Chemistry, University of Wollongong, Australia 1

2 ICOS Atmospheric Demonstration Experiment Four atmospheric stations Network calibration via the CAL Centralized data evaluation in the ATC Independent and comprehensive QC by Univ. Heidelberg 2

3 Atmospheric Inspection Team Equipment: In-situ FTIR spectrometer for CO 2, CH 4, CO and N 2 O analysis Independent pumping and drying system Standard gases calibrated by the CAL (MPI-BGC) Spare intake lines were provided by the stations 3

4 CO 2 comparison FTIR & GC in Heidelberg 4 23.Apr 12: 24.Apr : 24.Apr 12: 25.Apr : 25.Apr 12: FTIR GC A 211 CO2 [µmol/mol]

5 23.Apr 12: 24.Apr : 24.Apr 12: 25.Apr : 25.Apr 12: CO 2 comparison FTIR & GC in Heidelberg FTIR GC 211 A 5 CO2 [µmol/mol]

6 45 Exponentially smoothed FTIR measurements FTIR GC FTIR smoothed Apr 12: 24.Apr : 24.Apr 12: 25.Apr : 25.Apr 12: 211 A 6 CO2 [µmol/mol]

7 CO 2 comparison in Heidelberg April to May A 7 CO2 [µmol/mol] GC-FTIR

8 1 9 8 CO 2 frequency distribution Heidelberg, April to May 211 Lorentz Gauss frequency count CO 2 difference CO 2 [µmol/mol] GC - FTIR 8

9 1 9 8 CO 2 frequency distribution Heidelberg, April to May 211 Lorentz Gauss frequency count CO 2 difference Gauss fit: mean =.2 µmol/mol 1σ =.7 µmol/mol CO 2 [µmol/mol] GC - FTIR 9

10 1 9 8 CO 2 frequency distribution Heidelberg, April to May 211 Lorentz Gauss frequency count CO 2 difference Gauss fit: mean =.2 µmol/mol 1σ =.7 µmol/mol CO 2 [µmol/mol] GC - FTIR 1

11 1 9 8 CO 2 frequency distribution Heidelberg, April to May 211 IQR Lorentz Gauss frequency count CO 2 difference Gauss fit: mean =.2 µmol/mol 1σ =.7 µmol/mol IQR =.27 µmol/mol CO 2 [µmol/mol] GC - FTIR 11

12 Summary of the initial test phase in Heidelberg Buffer systems are indispensible when comparing sniff -like GC measurements to a nearly continuous measurement system. The buffer inherent smoothing needs to be taken into account for data evaluation. Initial CO 2 and CH 4 comparison between GC and FTIR in Heidelberg show that we are able to reach the WMO compatibility targets. 12

13 Cabauw station visit: May/June

14 Intake line test at Cabauw and Heidelberg 14

15 .1 Station STDs measured with the FTIR Cabauw STD FTIR Target 5 Cabauw STD 4 FTIR Target 3 CO 2 [µmol/mol] assigned - FTIR CO 2 assigned [µmol/mol] CH 4 [nmol/mol] assigned-ftir off scale CH 4 assigned [nmol/mol] 15

16 .1 Station STDs measured with the FTIR Cabauw STD FTIR Target 5 Cabauw STD 4 FTIR Target 3 CO 2 [µmol/mol] assigned - FTIR CH 4 [nmol/mol] assigned-ftir CO 2 assigned [µmol/mol] CH CO 2 [µmol/mol] 4 [nmol/mol] -4 off scale CH 4 assigned [nmol/mol] FTIR Target HD CBW HD

17 Overview of the entire comparison record for CBW 43 CO 2 CRDS 42 CO 2 FTIR Smoothed CO 2 CRDS CO 2 [µmol/mol] Mai 29 Mai 31 Mai 2 Jun Jun 6 Jun 8 Jun 17

18 Time series of the CO 2 difference FTIR - CRDS Mai 29 Mai 31 Mai 2 Jun 4 Jun 6 Jun 8 Jun 1 Jun CO2 [µmol/mol] FTIR-CRDS

19 CO 2 difference and hourly CO 2 change rate 31 Mai 2 Jun 4 Jun 6 Jun 8 Jun 1 Jun 29 Mai CO2 [µmol/mol] FTIR-CRDS /dt [µmol/mol/h] dco2 27 Mai

20 Selection criteria: hourly CO 2 change < 15 [µmol/mol/h] selected rejeced CO2 [µmol/mol] FTIR-CRDS selected rejeced dco2 /dt [µmol/mol/h] 27 Mai 29 Mai 31 Mai 2 Jun 4 Jun 6 Jun 8 Jun 1 Jun 211 2

21 Frequency distribution CO 2 differences FTIR-CRDS frequency count CO 2 difference Lorentz Gauss Gauss fit: mean =.19 µmol/mol 1σ =.8 µmol/mol IQR =.14 µmol/mol CO 2 [µmol/mol] FTIR-CRDS 21

22 OPE station visit: July/August

23 OPE station standards.1 Cabauw STD FTIR Target 2 Cabauw STD FTIR Target.5 1 CO 2 [µmol/mol] assigned - FTIR. -.5 CH 4 [nmol/mol] assigned-ftir CO 2 assigned [µmol/mol] CH 4 assigned [nmol/mol] 23

24 OPE station standards.1 Cabauw STD FTIR Target 2 Cabauw STD FTIR Target.5 1 CO 2 [µmol/mol] assigned - FTIR. -.5 CH 4 [nmol/mol] assigned-ftir CO 2 assigned [µmol/mol] CH 4 assigned [nmol/mol] CH CO 2 [µmol/mol] 4 [nmol/mol] FTIR Target HD OPE HD

25 Overview of the entire comparison record for OPE 42 CO 2 CRDS CO 2 FTIR Smoothed CO 2 CRDS Jul 24 Jul 27 Jul 3 Jul 2 Aug 5 Aug 8 Aug 11 Aug CO2 [µmol/mol]

26 Frequency distribution CO 2 differences FTIR-CRDS 1 Lorentz Gauss frequency count CO 2 difference Gauss fit: mean = -.6 µmol/mol 1σ =.12 µmol/mol IQR =.19 µmol/mol CO 2 [µmol/mol] FTIR-CRDS 26

27 Comparison to travelling instrument reveals periodic features 396 CO 2 CRDS 394 CO 2 FTIR Smoothed CO 2 CRDS Jul 6: 23.Jul 8: 23.Jul 1: 23.Jul 12: 23.Jul 14: 23.Jul 16: CO2 [µmol/mol]

28 CO 2 summary means and standard deviations.3 HD CBW OPE CO 2 [µmol/mol] station - traveling FTIR Apr Mai Jun Jul Aug Sep

29 CH 4 summary means and standard deviations 2 HD OPE CBW CH 4 [nmol/mol] station - traveling FTIR Apr Mai Jun Jul Aug

30 Summary Two continuous stations have been successfully validated by the travelling FTIR. Additional tests are needed to identify the origin for observed differences Comprehensive intake system tests have to be developed and should be routinely implemented Quantitative measure for non-gaussian distributions need to be defined High temporal resolution of the comparison data reveals very valuable information on system performance Comprehensive quality control using a travelling instrument is possible and strongly recommended. 3

31 Planed ICOS network 3 atmospheric stations 2 month per validation => 5 years for one entire check Acknowledgment: Funding was provided from ICOS PP (European union) 31

32 Sensitivity of the 1σ scattering against hourly CO 2 change rate.1.9 1σ Gauss fit [µmol/mol] FTIR-CRDS CO 2 difference Theoretical limit due to noise of both instruments dco 2 /dt [µmol/mol/h] selection cut off rate 32

33 CBW cucumber 33

34 CH 4 frequency distribution Heidelberg, April to May frequency count CH 4 difference Gauss fit: mean =.3 nmol/mol 1σ = 2.3 nmol/mol IQR = 3.6 nmol/mol CH 4 [nmol/mol] GC-FTIR 34

35 Frequency distribution CH 4 difference FTIR-CRDS frequency count CH 4 difference Gauss fit: mean = 1.1 nmol/mol 1σ =.72 nmol/mol IQR = 1.2 nmol/mol CH 4 [nmol/mol] FTIR-CRDS 35

36 Frequency distribution CH 4 difference FTIR-CRDS CO 2 [µmol/mol] CH 4 [nmol/mol] HD frequency count CH 4 difference FTIR target OPE HD Gauss fit: mean = 1.1 nmol/mol 1σ =.72 nmol/mol IQR = 1.2 nmol/mol CH 4 [nmol/mol] FTIR-CRDS 36

37 Comparing measurements with different turn-over constants Buffered GC FTIR CRDS τ = 3 min τ = 3.5 min τ =.1min GC V=1L buffer Φ=.33L/min FTIR CDRS V=3.5L cell.35l cavity Φ=1 L/min Φ=.25L/min t 1 τ C( tm) = C( tm t) e dt τ 37

38 Frequency distribution CH 4 difference FTIR-CRDS frequency count CH 4 difference Gauss Lorentz Gauss fit: mean =.31 nmol/mol 1σ =.81 nmol/mol IQR = 1.47 nmol/mol CH 4 [nmol/mol] FTIR-CRDS 38

39 Response of the buffered GC system to a concentration step change 35 GC measurement 3 CO 2 [µmol/mol] :3 : :3 1: 1:3 2: 2:3 3: 3:3 elapsed time since step change [h] 39

40 Exponentially smoothed input function 35 3 GC measurement Exponential smoothing CO 2 [µmol/mol] :3 : :3 1: 1:3 2: 2:3 3: 3:3 elapsed time since step change [h] 4

41 End-to-end Quality Control using travelling Instrumentation Within the ICOS Demo Experiment an inspection team was formed equipped with mobile instrumentation to perform independent measurements over a few weeks, in parallel to routine observations. Two atmospheric stations have been visited: Cabauw, NL, May 24 th to June 9 th 211 OPE, France, July 25 th to August 9 th

42 Intake line test 42